Stanford Classifer

A classifier is a machine learning tool that will take data items and place them into one of k classes. A probabilistic classifier, like this one, can also give a probability distribution over the class assignment for a data item. This software is a Java implementation of a maximum entropy classifier. Maximum entropy models are otherwise known as conditional loglinear models, and are essentially equivalent to multiclass logistic regression models (though parameterized slightly differently, in a way that is advantageous with sparse explanatory feature vectors). The classification method is described in:

Christopher Manning and Dan Klein. 2003. Optimization, Maxent Models, and Conditional Estimation without Magic. Tutorial at HLT-NAACL 2003 and ACL 2003. [pdf slides] [pdf handouts]

Version 2 of the classifier was developed by Anna Rafferty, Alex Kleeman, Jenny Finkel, and Christopher Manning.

The software requires requires Java (JDK1.5+). As well as API access, the program includes an easy-to-use command-line interface, ColumnDataClassifier, for building maximum entropy models. Its features are especially suited to building models over text data, but it also supports numeric variables.

Licensing. The Stanford Classifier is available for download, licensed under the GNU General Public License (v2 or later). Source is included. The Stanford Classifier code is dual licensed (in a similar manner to MySQL, etc.). Open source licensing is under the full GPL, which allows many free uses. For distributors of proprietary software, commercial licensing is available. If you don't need a commercial license, but would like to support maintenance of these tools, we welcome gift funding.

The download is a 1.3 MB zipped file. If you unpack that file, you should have everything needed, including example files and documentation. Start by reading the README.txt file. Send any questions or feedback to


A detailed introduction to the classifier is available on our Wiki page.

Mailing Lists

We have 3 mailing lists for the Stanford Classifier, all of which are shared with other JavaNLP tools (with the exclusion of the parser). Each address is at

  1. java-nlp-user This is the best list to post to in order to ask questions, make announcements, or for discussion among JavaNLP users. You have to subscribe to be able to use it. Join the list via this webpage or by emailing (Leave the subject and message body empty.) You can also look at the list archives.
  2. java-nlp-announce This list will be used only to announce new versions of Stanford JavaNLP tools. So it will be very low volume (expect 1-3 message a year). Join the list via via this webpage or by emailing (Leave the subject and message body empty.)
  3. java-nlp-support This list goes only to the software maintainers. It's a good address for licensing questions, etc. For general use and support questions, please join and use java-nlp-user. You cannot join java-nlp-support, but you can mail questions to

Download Stanford Classifier version 3.3.1

Release history

3.3.1 2014-01-04 Bugfix release
3.3.0 2013-11-12 Updated for compatibility with other Stanford releases
3.2.0 2013-06-20 Updated for compatibility with other Stanford releases
2.1.8 2013-04-04 Updated for compatibility with other Stanford releases
2.1.7 2012-11-11 Pair of word features added
2.1.6 2012-07-09 Minor bug fixes
2.1.5 2012-05-22 Updated for compatibility with other Stanford releases
2.1.4 2012-03-09 Bugfix for svmlight format
2.1.3 2011-12-22 Updated for compatibility with other Stanford releases
2.1.2 2011-09-14 Change ColumnDataClassifier to be an object with API rather than static methods; ColumnDataClassifier thread safe
2.1.1 2011-06-19 Updated for compatibility with other Stanford releases
2.1 2011-05-15 Updated with more documentation
2.0 2007-08-15 New command line interface, substantial increase in options and features (updated on 2007-09-28 with a bug fix)
1.0 2003-05-26 Initial release